JP6090137B2 - Biaxially stretched polypropylene film - Google Patents

Description

  The present invention relates to a biaxially stretched polypropylene film that is excellent in adhesion and peelability to an object to be protected and reduces foreign matter contamination, voids, and air voids when bonded. In particular, the present invention relates to a protective material or a release material used in a manufacturing process of an electronic component or an electronic substrate, a manufacturing process of a thermosetting resin member such as a fiber reinforced plastic, or a manufacturing process of a photosensitive film. More specifically, it is particularly useful for release films, release liners, carriers during material production, protective materials and separator films thereof, etc., and has excellent releasability, smoothness, transparency, and rollability, and rough surfaces. This relates to a biaxially stretched film in which the smoothness of the smooth surface is not impaired.

  Biaxially stretched polypropylene films are widely used as industrial material films including packaging because they are excellent in light weight, thermal stability and mechanical properties. In particular, in recent years, the low surface energy of polypropylene film has been used to protect electronic components, electronic substrate manufacturing processes, fiber reinforced plastics and other thermosetting resin member manufacturing processes, and photosensitive film manufacturing processes. Widely used in materials and mold release materials.

  As a technique for improving the release performance while maintaining the thermal stability and mechanical properties of the polypropylene film, for example, a technique in which a silicone release agent is applied to a low heat shrinkage polypropylene film is generally widely known ( For example, Patent Document 1). However, a film coated with a silicone-based release agent has a problem that it is not preferable for electronic parts because silicone transfer occurs when used as a release material (separator film) for a protective film of an electronic device or the like. Therefore, a non-silicone (coating) film is strongly demanded as a protective film used in the manufacturing process of electronic parts and electronic substrates.

  As a protective film used in the manufacturing process of electronic parts, electronic substrates and photosensitive materials, it is also necessary that there are few foreign matter projections due to fish eyes, defects, etc., and as such a polypropylene protective film, An unstretched film having a specific physical property value by blending an α-olefin copolymer elastomer has been proposed (for example, Patent Document 2). However, this film is an opaque film with a high haze, and is inappropriate when high visibility of the protected object is required. In addition, there is a problem that the smoothness is insufficient and cannot be used for applications that require high smoothness on the bonding surface with the non-protective body.

  Patent Document 3 discloses an unstretched film that defines the average roughness of both surfaces. This film also tends to be opaque with high haze, and is unsuitable when high visibility of the protected object is required. Furthermore, when stored by winding, the pressure applied to the film inside the winding causes steep rough protrusions on the roughened surface to generate minute dents on the smoothed surface (transfer of the roughened surface), and the object to be protected There was also a problem that a defect occurred in the bonding.

  If the film is roughened on both sides, both sides are originally rough, so even if the roughened surface is transferred by the pressure applied to the film inside the winding and a minute dent is generated, there is a problem. Although it is difficult to achieve this, it cannot be used for applications where high smoothness is required for the surface to be bonded to the object to be protected. On the other hand, a smooth film on both sides is not likely to impair the smoothness due to the roughened surface being transferred during winding and storage, but it is prone to problems in winding properties such as blocking, winding slip, and wrinkles. However, the air is not uniformly removed from the winding and becomes an air reservoir, and a problem such that the film is uneven in the winding is likely to occur. A film with one side roughened can achieve both smoothness and winding property, but if the roughened surface is transferred to the smooth surface, the smoothness of the smooth surface is impaired. There is a need for a technique that does not cause the transfer of the roughened surface while maintaining it.

Japanese Patent Laid-Open No. 10-226781 JP 2010-184990 A JP 2010-42665 A

  The present invention relates to a release film, a release liner, and a carrier used in the production of materials, which are used in the production process of electronic components, electronic substrates, the production process of thermosetting resin members such as fiber reinforced plastics, the production process of photosensitive films, etc. Particularly useful for protective materials and separator films, etc., with low contamination of foreign matter on the object to be protected, excellent peelability, high transparency and smoothness, and low occurrence of blocking, wrinkles, unevenness, etc. The object is to provide a biaxially stretched film having matching performance.

As a result of intensive studies to solve such problems, it has been found that the above problems can be solved by using a biaxially stretched polypropylene film including an outermost layer having different specific surface roughness.
That is, the present invention provides the following biaxially stretched polypropylene film.

Item 1. A laminated film having an outermost layer A layer and an outermost layer B layer having different surface roughness, wherein the A layer is formed from a resin composition containing a propylene-based polymer, and satisfies the following (a) to (c):
(A) The value (Sp) of the maximum peak height of the outer surface is 0.1 μm or less,
(B) The root mean square (Sq) of the height data of the outer surface is 0.01 μm or less, and (c) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 μm. Less than,
B layer is formed from the resin composition containing a propylene polymer and an α-olefin polymer, and the following (d) to (f):
(D) The value (Sp) of the maximum peak height of the outer surface is 0.5 μm or less,
(E) The root mean square (Sq) of the height data of the outer surface is 0.01 to 0.05 μm, and (f) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01-0.05 μm,
A biaxially oriented polypropylene film that meets the requirements.

  Item 2. Item 2. The biaxially stretched polypropylene film according to Item 1, having at least one intermediate layer between the A layer and the B layer.

  Item 3. Item 3. The biaxially stretched polypropylene film according to Item 2, wherein the intermediate layer is formed from a resin composition containing a propylene-based polymer.

  Item 4. Item 4. The biaxially stretched polypropylene film according to any one of Items 1 to 3, wherein the total thickness is 10 to 150 μm.

  Item 5. Item 5. The biaxially stretched polypropylene film according to any one of Items 1 to 4, comprising 5 to 30% by mass of an α-olefin polymer in the resin composition forming the B layer.

  Item 6. Item 6. The biaxially stretched polypropylene film according to any one of Items 1 to 5, wherein the α-olefin polymer contained in the resin composition forming the B layer is a butene polymer.

  Item 7. Item 7. The biaxially stretched polypropylene film according to Item 6, wherein the butene polymer is a 1-butene / ethylene copolymer.

  Item 8. Item 6. The biaxially stretched polypropylene film according to any one of Items 1 to 5, wherein the α-olefin polymer contained in the resin composition forming the B layer is a 4-methyl-1-pentene polymer. .

  Item 9. Item 10. The biaxially stretched polypropylene film according to any one of Items 1 to 8, wherein the ash content in the film is 100 ppm or less.

Item 10. Item 10. The biaxially stretched polypropylene film according to any one of Items 1 to 9, wherein the number of fish eyes having an area of 0.0045 mm ² or more is 700 / m ² or less.

Item 11. Item 11. A method for producing a biaxially stretched polypropylene film according to any one of Items 1 to 10, wherein the following steps (i) to (iv):
(I) A step of preparing a resin composition for forming an A layer and a B layer, and an intermediate layer as necessary;
(Ii) a step of filtering the resin composition obtained in step (i) after extrusion,
(Iii) a step of laminating and molding the resin composition obtained in step (ii) to obtain a cast sheet;
(Iv) a step of biaxially stretching the cast sheet obtained in step (iii);
And in the step (ii), filtration is performed with a filter having a filtration accuracy of 20 μm or less.

  The biaxially stretched polypropylene film of the present invention is excellent in adhesion, peelability, smoothness and transparency. Therefore, as a protective film and / or non-silicone separator film used in the manufacturing process of electronic components, electronic substrates, the manufacturing process of thermosetting resin members such as fiber reinforced plastics, the manufacturing process of photosensitive films, etc. Is preferred.

  Moreover, since the biaxially stretched polypropylene film of this invention is excellent in winding property, productivity is also good.

It is the image which processed the surface shape data of the smooth surface of the biaxially stretched polypropylene film obtained in Example 1 by VS-Viewer. It is the image which processed the surface shape data of the roughening surface surface of the biaxially stretched polypropylene film obtained in Example 1 by VS-Viewer. It is the image which processed the surface shape data of the roughening surface of the biaxially-stretched polypropylene film obtained by the comparative example 1 by VS-Viewer. It is the image which processed the surface shape data of the roughening surface of the biaxially-stretched polypropylene film obtained by the comparative example 2 by VS-Viewer.

1. Biaxially stretched polypropylene film The biaxially stretched polypropylene film of the present invention is a laminated film having an outermost layer A layer and an outermost layer B layer having different surface roughnesses,
A layer is formed from a resin composition containing a propylene polymer, and satisfies the following (a) to (c),
(A) The value (Sp) of the maximum peak height of the outer surface is 0.1 μm or less,
(B) The root mean square (Sq) of the height data of the outer surface is 0.01 μm or less, and (c) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 μm. Less than,
B layer is formed from the resin composition containing a propylene polymer and an α-olefin polymer, and the following (d) to (f):
(D) The value (Sp) of the maximum peak height of the outer surface is 0.5 μm or less,
(E) The root mean square (Sq) of the height data of the outer surface is 0.01 to 0.05 μm, and (f) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 to 0.05 μm is satisfied.

  The A layer is the outermost layer on the surface (smooth surface) side to be bonded to the object to be protected, and the B layer constitutes the outermost layer on the opposite surface (roughened surface) side. At least one intermediate layer may be provided between the A layer and the B layer.

1-1. A layer (the outermost layer on the surface (smooth surface) to be bonded to the protected object)
The A layer in the biaxially stretched polypropylene film of the present invention is the outermost layer on the side to be bonded to the protected body.

  The A layer is formed from a resin composition containing a propylene polymer.

(1) Propylene polymer Examples of the propylene polymer include a propylene homopolymer (homopolypropylene) and a propylene-ethylene copolymer having a small amount of ethylene as a copolymerization component. From the viewpoint of improving releasability, it is preferable to use a propylene homopolymer (homopolypropylene). Two or more types of propylene-based polymers can be mixed and used, but one type of propylene-based polymer is used to suppress the generation of fish eyes due to the difference in fluidity of each raw material and to improve smoothness. The embodiment used is preferred.

  As the homopolypropylene, an isotactic polypropylene homopolymer is preferable from the viewpoint of improving peelability. Among them, the isotactic meso pentad fraction (mmmm) is preferably 90% to 97%, more preferably 91% to 95%.

  The isotactic mesopentad fraction (mmmm) is the degree of stereoregularity obtained by high temperature nuclear magnetic resonance (NMR) measurement. When the isotactic meso pentad fraction (mmmm) is 90% or more, it is easy to prevent contamination of the non-protected body by the amorphous component, and the releasability tends to be improved. Further, when the isotactic mesopentad fraction (mmmm) is 97% or less, the stretchability is improved, and there is a tendency that a film with little variation in smoothness and thickness can be obtained.

  The copolymerization ratio of ethylene in the propylene-ethylene copolymer is preferably 5% by weight or less. The propylene-ethylene copolymer may be a random copolymer or a block copolymer.

  The MFR of the propylene polymer can be measured according to JIS K7210 (1999). Specifically, it is preferably 2 to 15 g / 10 minutes, more preferably 2.5 to 10 g / 10 minutes, under measurement conditions of a temperature of 230 ° C. and a load of 21.18 N. By setting it as 2 g / 10min or more, the filterability of the melted resin composition can be improved in the extrusion / filtration process when forming a film. Moreover, it can be set as a film with few dispersion | variation in smoothness and thickness by setting it as 15 g / 10min or less.

  The propylene polymer can be obtained by a known polymerization method. Examples of the polymerization method include a gas phase polymerization method, a bulk polymerization method, and a slurry polymerization method. There is no restriction | limiting in particular as a polymerization catalyst, Although titanium-type catalysts, such as a Ziegler catalyst, can be used conveniently, Especially the propylene-type polymer polymerized using the single site catalyst is used preferably. By polymerizing using a single site catalyst, it is easy to obtain a propylene-based polymer having a narrow molecular weight distribution, and since there is little content of low molecular weight components, it is easy to prevent contamination of non-protected materials.

  A single site catalyst refers to a catalyst composed of substantially homogeneous polymerization active sites, specifically a metallocene transition metal compound (so-called Kaminsky catalyst) or a nonmetallocene transition metal compound (Brookhardt system). A polymerization catalyst composed of a catalyst, a phenoxyimine-based complex, and the like) and a co-catalyst (such as methylaluminoxane and a boron compound).

  As a preferable single site catalyst, a metallocene catalyst having a metallocene transition metal compound as a main component can be exemplified. As the metallocene catalyst, a non-bridged metallocene catalyst such as biscyclopentadienylzirconium dichloride or a substituted product thereof can also be used.

  The ash content in the propylene polymer is preferably 100 ppm or less, more preferably 50 ppm or less, further preferably 30 ppm or less, and particularly preferably 20 ppm or less. When it is 100 ppm or less, it is easy to suppress the generation of fish eyes.

  The ash content of the propylene polymer is often derived from a polymerization catalyst residue and a neutralizing agent (chlorine scavenger) used in the propylene polymer. Therefore, it is effective to reduce the polymerization catalyst residue in the washing step after polymerization. As the neutralizing agent (chlorine scavenger), known neutralizing agents such as calcium stearate and hydrotalcite can be used, but the addition amount is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. 50 ppm or less is particularly preferable. By setting it to 300 ppm or less, it is easy to suppress the generation of fish eyes and to prevent contamination of the non-protected body by the neutralizing agent.

(2) In order to give chemical stability to the resin composition which forms the other compounding component A layer, you may mix | blend antioxidant. Antioxidant has at least a role as a primary agent blended for the purpose of suppressing deterioration due to heat and oxidation in an extruder during production of a biaxially oriented polypropylene film, and with time when used for a long time. There is a role as a secondary agent blended for the purpose of suppressing deterioration. Depending on these two roles, different types of antioxidants may be used, or one type of antioxidant may have two roles.

  When different types of antioxidants are used, for example, 2,6-di-tert-butyl-p-cresol (generic name: BHT) is used as the primary agent for the purpose of suppressing deterioration in the extruder. It is preferable to add about 1000 to 3000 ppm in the resin composition. Most of the antioxidant blended for this purpose is consumed in the molding process in the extruder, and hardly remains in the biaxially oriented polypropylene film. Therefore, generally, the remaining amount is less than 100 ppm, which is preferable in that there is almost no contamination of the non-protected body by the antioxidant.

  As the secondary agent, known antioxidants can be used, and examples thereof include phenol-based, hindered amine-based, phosphite-based, lactone-based, and tocopherol-based thermal stabilizers and antioxidants. Specifically, dibutylhydroxytoluene, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris ( 3,5-di-t-butyl-4hydroxy) benzene, tris (2,4-di-t-butylphenyl) phosphite and the like can be mentioned. More specifically, Irganox (registered trademark) 1010, Irganox (registered trademark) 1330, and Irgafos (registered trademark) 168, which are antioxidants manufactured by Ciba Specialty Chemicals Co., Ltd., can be mentioned.

  Among them, at least one selected from phenolic antioxidants or a combination thereof, a combination of phenolic and phosphite, a combination of phenolic and lactone, a combination of phenolic, phosphite and lactone However, the effect which suppresses deterioration with time at the time of using a film for a long term can be provided, and it is preferable.

  The content of the antioxidant as the secondary agent is preferably from 300 ppm to 2500 ppm, more preferably from 500 ppm to 1500 ppm. By setting it to 300 ppm or more, it is easy to impart the effect of suppressing deterioration over time when the film is used for a long time, and by setting it to 2500 ppm or less, it is easy to prevent contamination of the non-protected body by the antioxidant.

  In addition, the resin composition forming the A layer has other various additives (stabilizers such as ultraviolet absorbers, crystal nucleating agents, plasticizers, flame retardants, and the like within the range not impairing the effects of the present invention. You may add an antistatic agent, a coloring agent, etc.).

(3) Surface characteristics As for A layer of this invention, the outer surface (surface bonded with a to-be-protected body; smooth surface) is following (a)-(c);
(A) The value (Sp) of the maximum peak height of the outer surface is 0.1 μm or less,
(B) The root mean square (Sq) of the height data of the outer surface is 0.01 μm or less, and (c) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 μm. The following is characterized.

  Here, the maximum peak height value (Sp) is a parameter “Maximum peak height” described in ISO25178. The root mean square (Sq) of the surface height data is a parameter “Root mean square height” described in ISO25178. The protruding peak height (Rpk) in the load curve is JIS B-0671-2: 2002, which is calculated from the height characteristic according to the linear load curve, and the protruding peak height above the core portion of the roughness curve. Is the average height. The (Rpk) is an index that makes it possible to determine the state of protruding protrusions that have a large effect on contact with the object to be protected while removing the influence of continuous undulations on the film surface.

  The height value (Sp) of the maximum peak, the root mean square (Sq) of the height data, and the protruding peak height (Rpk) in the load curve are, for example, a contact type using a stylus, visible light reflection, laser It can be measured by a non-contact method using optical interference, an atomic force phase difference measurement using a scanning probe microscope (SPM / AFM), or the like. Specifically, for example, it can be measured by the method described in the examples.

  When (Sp) is greater than 0.1 μm, or (Sq) or (Rpk) is greater than 0.01 μm, abnormal bonding may occur such as voids when bonding to the protected object. When the film is peeled off from the object to be protected, there is a tendency that a problem such as generation of adhesive residue due to the roughness of the film occurs. (Sp) is more preferably 0.05 μm or less, and still more preferably 0.03 μm or less. Although a minimum is not specifically limited, About 0.01 micrometer or more is preferable. Further, preferable (Sq) and (Rpk) are 0.008 μm or less, and a more preferable range is 0.006 μm or less. Although a minimum is not specifically limited, About 0.003 micrometer or more is preferable.

  The thickness of the A layer is preferably 3 μm or more. By setting the thickness to 3 μm or more, it is possible to easily form a highly smooth surface by blocking the influence of the roughness on the roughened surface side. More preferably, it is 5 μm or more. The upper limit is determined in consideration of the total thickness of the film and the thickness of the B layer, and in the case of providing an intermediate layer, including the thickness, but is preferably approximately 30 μm or less.

  The thickness of each layer of the film can be measured by confirming the boundary of the layer by observing a cross section of the film under a microscope, but it may be difficult to confirm the boundary depending on the lamination method. In that case, melt extrusion of each layer single layer is performed in advance to measure the resin discharge amount, and the calculated value calculated from the total thickness of the film and the discharge amount of each layer can be substituted.

1-2. B layer (outermost layer on the opposite surface (roughened surface) side)
The B layer in the biaxially stretched polypropylene film of the present invention is the outermost layer on the side opposite to the outermost layer bonded to the protected body.

  The B layer is formed from a resin composition containing a propylene polymer and an α-olefin polymer.

(1) Propylene-based polymer As the propylene-based polymer, for example, the same propylene-based polymer as in the A layer can be mentioned. The propylene-based polymer used for forming the A layer and the propylene-based polymer used for forming the B layer may be the same or different. From the viewpoint that it is easy to suppress the problem of contaminating the non-protecting body by exuding the components and contaminating the smooth surface, it is preferable that they are the same.

  As a content rate of a propylene-type polymer, 70-95 mass% is preferable in the polymer composition (100 mass%) which forms B layer, 80-92 mass% is more preferable, 85-90 mass% is further preferable.

(2) α-Olefin Polymer As the α-olefin polymer, for example, a propylene polymer, a butene polymer, a hexene polymer, an octene polymer, a decene polymer, 4-methyl-1 -A pentene polymer etc. are mentioned. These polymers are produced by polymerizing known monomers in the presence of known olefin polymerization catalysts, such as vanadium-based catalysts, titanium-based catalysts, magnesium-supported titanium-based catalysts, metallocene-based catalysts, and the like. . Examples of the known monomer include α-olefins having 3 to 20 carbon atoms. Specifically, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3-ethyl-1-pentene 4,4-dimethyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1 -Decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and the like can be mentioned. These α-olefins can be used singly or in combination of two or more.

  As the α-olefin polymer, it is particularly preferable to use a butene polymer or a 4-methyl-1-pentene polymer alone or in combination of two or more.

  As the butene polymer, 1-butene homopolymer, or 1-butene as a main component, ethylene, propylene, hexene, 4-methyl-1-pentene and / or other olefins were copolymerized therewith. Contains things. The copolymerization mode includes both random copolymerization and block copolymerization.

  Specifically, 1-butene / ethylene copolymer, 1-butene / propylene copolymer, 1-butene / 1-hexene copolymer, 1-butene / 4-methyl-1-pentene copolymer, 1 -Butene / 1-octene copolymer, 1-butene / 1-decene copolymer, 1-butene / 1,4-hexadiene copolymer, 1-butene / dicyclopentadiene copolymer, 1-butene / 5 -Two-component copolymers such as ethylidene-2-norbornene copolymer, 1-butene-2,5-norbornadiene copolymer, 1-butene-5-ethylidene-2-norbornene copolymer, Butene / ethylene / propylene copolymer, 1-butene / ethylene / 1-hexene copolymer, 1-butene / ethylene / 1-octene copolymer, 1-butene / propylene / 1-octene copolymer, Bute・ Ethylene / 1,4-hexadiene copolymer, 1-butene / propylene / 1,4-hexadiene copolymer, 1-butene / ethylene / dicyclopentadiene copolymer, 1-butene / propylene / dicyclopentadiene copolymer Polymer, 1-butene / ethylene / 5-ethylidene-2-norbornene copolymer, 1-butene / propylene / 5-ethylidene-2-norbornene copolymer, 1-butene / ethylene / 2-norbornadiene copolymer 1-butene / propylene / 2-norbornadiene copolymer, 1-butene / ethylene / 5-ethylidene-2-norbornene copolymer, 1-butene / propylene / 5-ethylidene-2-norbornene copolymer And a multi-component copolymer such as

  Among these butene-based copolymers, it is particularly preferable to use 1-butene / ethylene copolymer because (Sq) and (Rpk) on the roughened surface are easily within the specific range of the present invention. Examples of commercially available 1-butene / ethylene copolymers are available from Mitsui Chemicals, Inc., Tuffmer (registered trademark) BL3450, and the like.

  The MFR of the butene polymer can be measured according to JIS K7210 (1999). Specifically, it is preferably 3 to 20 g / 10 minutes and more preferably 5 to 15 g / 10 minutes under the measurement conditions of a temperature of 230 ° C. and a load of 21.18 N. By setting the amount within this range, the fluidity of the propylene-based polymer becomes close, uniform melt kneading is performed, and coarse protrusions are hardly generated on the roughened surface, and (Sp), (Sq), and (Rpk) ) Within a specific range of the present invention.

  When the melting point of the butene polymer is usually 60 to 130 ° C., preferably 100 to 130 ° C., the stretchability is excellent, and (Sp), (Sq) and (Rpk) are easily set within the specific range of the present invention. .

  As the 4-methyl-1-pentene polymer, a homopolymer of 4-methyl-1-pentene or a polymer mainly composed of 4-methyl-1-pentene and copolymerized with other olefins. contains. The copolymerization mode includes both random copolymerization and block copolymerization.

  Examples of the other monomer copolymerized with 4-methyl-1-pentene include ethylene and α-olefin having 3 to 20 carbon atoms excluding 4-methyl-1-pentene. Specifically, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4,4-dimethyl-1 -Pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, -Tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and the like. Of these, α-olefins having 3 to 8 carbon atoms are preferable, and α-olefins having 3 to 4 carbon atoms and 3-methyl-1-pentene are more preferable. These α-olefins can be used singly or in combination of two or more.

  The MFR of these 4-methyl-1-pentene polymers can be measured according to JIS K7210 (1999). Specifically, it is preferably 15 to 150 g / 10 minutes, more preferably 20 to 100 g / 10 minutes, under measurement conditions of a temperature of 260 ° C. and a load of 49.05 N.

  By setting it within this range, it becomes close to the fluidity of the propylene-based polymer, uniform melt kneading is performed, and it is difficult for coarse protrusions to occur on the roughened surface, and (Sp), (Sq), and (Rpk) are It becomes easy to make the invention specific range.

  The melting point of the 4-methyl-1-pentene polymer is preferably 230 ° C. or lower, and moreover, the melting point of the propylene polymer used for the resin composition forming the B layer is 225 ° C. or lower. In addition to being excellent, (Sp), (Sq) and (Rpk) can be easily set within the specific range of the present invention.

  As a commercially available 4-methyl-1-pentene polymer, for example, TPX (registered trademark) MX002O, MX004, RT31, DX845, etc., available from Mitsui Chemicals, Inc. are available.

  The content ratio of the α-olefin polymer is 5 to 30% by mass in the polymer composition (100% by mass) forming the B layer, more preferably 8 to 20% by mass, and still more preferably 10 to 10% by mass. 15% by mass. When 5 to 30% by mass is contained, (Sp), (Sq) and (Rpk) are likely to be within the specific range of the present invention.

(3) In the resin composition forming the other compounding component B layer, the same antioxidant as that blended in the resin composition forming the A layer, and the like, within the range not inhibiting the effect of the present invention These additives may be added (stabilizers such as ultraviolet absorbers, crystal nucleating agents, plasticizers, flame retardants, antistatic agents, colorants, etc.).

(4) Surface characteristics The outer layer (roughened surface) of the B layer of the present invention has the following (d) to (f):
(D) The value (Sp) of the maximum peak height of the outer surface is 0.5 μm or less,
(E) The root mean square (Sq) of the height data of the outer surface is 0.01 to 0.05 μm, and (f) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 to 0.05 μm is satisfied.
In addition, the measuring method of the said value is the same as the measuring method of the outer surface of A layer.

  When (Sq) and (Rpk) are smaller than 0.01 μm, problems such as blocking, winding slip, and wrinkling are likely to occur, and the entrained air does not escape uniformly from the winding. The problem is that it becomes a reservoir and the film is uneven in the winding.

  Further, when (Sp) is larger than 0.5 μm, or (Sq) or (Rpk) is larger than 0.05 μm, when stored by winding, roughening occurs due to the pressure applied to the film inside the winding. A problem arises in that the “roughened surface transfer” problem occurs in which the rough projections with sharp surfaces cause minute dents on the smooth surface. If the smoothness of the smooth surface is deteriorated due to the transfer of the roughened surface, it causes a problem in bonding with the non-protected body.

A preferable range of (Sp) is 0.3 μm or less, and a more preferable range is 0.02 μm or less. A more preferable range of (Sq) and (Rpk) is 0.012 μm or more and 0.04 μm or less, and a further preferable range is 0.014 μm or more and 0.03 μm or less, and a particularly preferable range is 0.015 μm or more. 0.025 μm or less.
Further, the relationship between (Sq) and (Rpk) is that when (Sq) ≧ (Rpk), there is a tendency that there are few steep coarse protrusions and a uniform roughened surface, and it is easier to suppress the transfer of the roughened surface. preferable.

  The thickness of the B layer is preferably 0.5 μm or more and 5 μm or less. When the thickness is increased, (Sp), (Sq) and (Rpk) tend to increase, and when the thickness is decreased, (Sp), (Sq) and (Rpk) tend to decrease. In order to set (Sp), (Sq), and (Rpk) to the above-mentioned range, it is preferable to be within this thickness range. More preferably, they are 1 micrometer or more and 4 micrometers or less, More preferably, they are 1.2 micrometers or more and 3 micrometers or less, Especially preferably, they are 1.4 micrometers or more and 2.5 micrometers or less.

1-3. Intermediate layer At least one intermediate layer may be further provided between the A layer and the B layer of the present invention, if necessary.

  The intermediate layer has a film thickness suitable for the purpose of use, adjustment of the film stiffness, elongation, and elastic modulus, or coloring to increase the visibility of the film as necessary, and stretchability to increase productivity. It is preferable to provide for adjustment of the above.

  An intermediate | middle layer can be formed with the resin composition containing the at least 1 sort (s) of polymer selected from the group which consists of an ethylene polymer, a propylene polymer, etc., for example. Among them, it is formed from a resin composition containing a propylene polymer as a main component in order to suppress fish eyes and to obtain good adhesion to the outermost layer on the smooth surface side and the outermost layer on the roughened surface side. It is preferable.

  As a propylene polymer, the same propylene polymer as A layer is mentioned, for example. The propylene-based polymer used for forming the A layer and the propylene-based polymer used for forming the intermediate layer may be the same or different. From the viewpoint of preventing peeling and curling due to temperature change, the same is preferable.

  As a content rate of a propylene polymer, 80 mass% or more is preferable in the polymer composition (100 mass%) which forms an intermediate | middle layer, and 90 mass% or more is more preferable.

  It is preferable to mix a crystal nucleating agent with the resin composition forming the intermediate layer. By blending the crystal nucleating agent, the transparency, thermal stability and / or mechanical properties of the film can be improved.

  The crystal nucleating agent is not particularly limited, and a publicly known fine particle type or dissolution type nucleating agent can be used. For example, examples of the fine particle type include talc-based and aluminum-based inorganic substances, and examples of the dissolution type include amide-based and sorbitol-based organic nucleating agents. Use of the dissolution type is preferred because it is difficult to cause clogging of the filter when the molten resin composition is filtered with a filter in the extrusion / filtration step when forming a film.

  The addition amount of the crystal nucleating agent may be an optimal amount for the crystal nucleating agent to be used, but is preferably 1000 ppm or less from the viewpoint of improving the smoothness of the film.

  In the resin composition forming the intermediate layer, the same antioxidants as those added to the resin composition forming the A layer and various additives (antioxidants and You may add stabilizers, such as a ultraviolet absorber, a plasticizer, a flame retardant, an antistatic agent, and a coloring agent. In particular, when providing the intermediate layer, it is preferable to add an additive to the resin composition forming the intermediate layer instead of the A layer and the B layer from the viewpoint of preventing contamination of the non-protected body by the additive.

1-4. Layer structure As the layer structure of the biaxially stretched polypropylene film of the present invention, a two-layer structure in which an A layer and a B layer are laminated, a three-layer structure in which an A layer / intermediate layer / B layer are laminated in this order, an A layer / Examples include a four-layer structure in which the intermediate layer / intermediate layer / B layer are stacked in this order, and a five-layer structure in which the layer A / intermediate layer / intermediate layer / intermediate layer / B layer are stacked in this order.

1-5. Film Physical Properties The total thickness of the biaxially stretched propylene film of the present invention is preferably 10 to 150 μm, more preferably 12 to 100 μm, and further preferably 15 to 80 μm. When the total thickness of the film is 10 to 150 μm, it is possible to obtain a film having excellent handling properties (film strength, elongation, rigidity, etc.) upon sticking to a protected body or peeling.

  The haze degree according to JIS-K7136 of the biaxially stretched polypropylene film of the present invention is preferably 0.5% to 8%, more preferably 1% to 5%, and further preferably 1.5% to 4%. In the transparent film, the haze degree changes due to light scattering on the surface. When the haze degree is within this range, the (Sp), (Sq), and (Rpk) of the roughened surface are within the above-mentioned range. It becomes easy to become.

  The transparency (minimum transparency) of the biaxially stretched polypropylene film of the present invention is preferably 40% or more, more preferably 50% or more, and further preferably 60% or more. The transparency can be measured with a transparency measuring instrument TM-1D manufactured by Murakami Color Research Laboratory. High transparency is effective when high visibility of the protected object is required. There is no particular upper limit, but it is about 85% or less.

In biaxially oriented polypropylene film of the present invention, the number of the results of counting the area 0.0045Mm ² or more fish eyes in terms of per 1 m ² is preferably 700 / ^{m 2} or less, 400 / ^{m 2} Or less, more preferably 200 / m ² or less, and particularly preferably zero.

  The fish eye in the film is a film product in which foreign substances, unmelted materials, oxidized deterioration products, etc. in the material when the film is produced are taken into the film product. In particular, when the outermost layer (A layer) on the smooth surface side has a lot of fish eyes, foreign matter contamination, voids, and air when bonded as protective films used in the manufacturing process of electronic parts, electronic substrates and photosensitive materials, etc. In order to cause voids, it is required to be as small as possible.

As a method of measuring the number and size of fish eyes, a known technique such as a method of capturing an image of a film surface using a CCD camera or the like and analyzing the image with a computer or the like can be used. ) If a fish eye counter manufactured by KK is used, fish eyes having an area of 0.000225 mm ² or more can be accurately counted.

  The ash contained in the biaxially stretched polypropylene film of the present invention is preferably 100 ppm or less, more preferably 50 ppm or less, still more preferably 30 ppm or less, and particularly preferably 20 ppm or less, from the viewpoint of suppressing fisheye.

2. Method for Producing Biaxially Stretched Polypropylene Film The biaxially stretched polypropylene film of the present invention was obtained by the steps of preparing a resin composition for forming an A layer and a B layer, and if necessary, an intermediate layer, and the preparation step. It has an extrusion / filtration process for extruding and filtering the resin composition, a cast sheet manufacturing process for producing a cast sheet by laminating and molding the obtained filtrate, and a stretching process for biaxially stretching the obtained cast sheet. It can be manufactured by a method.

(1) Preparation process The preparation process of B layer can be performed by dry blending or melt kneading (melt blending). In the A layer and the intermediate layer, when a plurality of raw material polymers are used, when an additive is mixed, it can be similarly performed by dry blending or melt kneading.
The dry blend has a simple process and is superior in production cost. However, at the time of preparing the B layer, the propylene polymer and the olefin polymer are kneaded more uniformly, and the outer surface (roughened surface) ( From the viewpoint of easily setting Sp), (Sq), and (Rpk) within the aforementioned ranges, melt kneading is preferable. In particular, melt kneading is suitable when the melting point of the α-olefin polymer is higher than the melting point of the propylene polymer, or when the MFR of the α-olefin polymer is lower than the melting point of the propylene polymer. .

  In the case of melt kneading, the resin (composition) temperature is preferably 200 ° C. or higher and 270 ° C. or lower. By setting it as 270 degrees C or less, the thermal deterioration of propylene-type resin can be suppressed and a fish eye can be suppressed. Moreover, it can knead | mix more uniformly by setting it as 200 degreeC or more, and it becomes easy to make (Sp), (Sq), and (Rpk) of a roughening surface into the above-mentioned range. In order to suppress thermal deterioration during kneading and mixing, an inert gas such as nitrogen may be purged into the kneader. It is also preferable to do so.

There are no particular restrictions on the melt kneader, and a single screw type, a twin screw type, or a multi-screw type can be used as appropriate. It is preferable to use a machine.
A raw material resin can be obtained by pelletizing the melt-kneaded resin to an appropriate size using a known granulator.

  On the other hand, as a mixing apparatus for dry blending, a batch type such as a tumbler or a wing mixer, or a continuous type measurement mixer can be preferably used.

(2) Extrusion / filtration process The extrusion / filtration process supplies the raw material polymer in the form of powder or pellets or the resin composition in the form of pellets prepared in the above preparation process to an extrusion molding machine, and heat-melts it. -After extrusion, it is performed by filtering with a filter.

  There is no restriction | limiting in particular in an extruder, A well-known thing can be used. For example, a uniaxial screw type, a biaxial screw type, or a multiaxial screw type can be used as appropriate.

  The resin (composition) temperature during extrusion is preferably 220 ° C. or higher and 270 ° C. or lower. By setting it as 270 degrees C or less, the thermal deterioration of a propylene polymer can be suppressed. Further, by setting the temperature to 220 ° C. or higher, kneading is more uniform, and (Sp), (Sq), and (Rpk) of the roughened surface are easily set to the above-described range, and the resin passes through the filter. Can improve sex. In order to suppress thermal deterioration during extrusion molding, the extruder may be purged with an inert gas such as nitrogen. It is also preferable to do so.

  The melt-extruded resin is filtered with a so-called polymer filter installed between the extruder and the T-die. In order to suppress fish eyes, it is preferable to use a filter having high filtration accuracy. The filtration accuracy should be as small as 20 μm (98% cut size) or less, preferably 10 μm or less, and more preferably 5 μm or less. However, the higher the filtration accuracy (the smaller the size), the higher the removal rate of minute foreign matters, but the resin differential pressure (pressure loss) at the entrance and exit of the polymer filter increases and the resin discharge tends to become unstable, so the filtration accuracy is When it is 1 μm or more, resin discharge is stable and preferable.

  The polymer filter may be installed in only one machine, but may be installed in multiple stages of two or more machines, and in particular, in multiple stages, when installing in stages from low filtration accuracy to high filtration precision, The resin differential pressure is difficult to increase, and stable ejection can be obtained, and filtration accuracy is also improved, which is preferable.

  As the filter medium used for the polymer filter, generally known filter media can be used without limitation. For example, a sintered metal nonwoven fabric (fiber sintered body), a laminated sintered wire mesh, a powder sintered body, etc. can be mentioned.

  Moreover, as a filter type, a leaf disk filter, a candle filter, a pack filter, or the like can be used without limitation.

  Among them, a leaf disk type filter using a sintered metal nonwoven fabric (fiber sintered body) can be preferably employed because the resin differential pressure is not increased and stable discharge is obtained and the service life is long.

(3) Cast sheet manufacturing process In the cast sheet manufacturing process for forming a cast sheet (raw fabric sheet) before stretching, the filtered resin composition of each layer is laminated and melt extruded from a T die.

  The filtered resin composition forms a configuration of A layer / if necessary, one or more intermediate layers / B layer using a resin merging device. The merging device is not particularly limited, but is a method of merging the resin composition in the polymer tube before the die of the T die, a feed block method of merging with a laminated unit provided in the resin introduction part of the die of the T die, T For example, a manifold lamination method in which both resins are laminated after widening in the die base. The laminated resin composition is extruded from the T die lip.

  The laminated resin melt-extruded from the T-die is brought into close contact with a cooling molding roll with an air knife, cooled and solidified, whereby an unstretched cast sheet is obtained. A plurality of cooling molding rolls may be used in order to increase the cooling efficiency. Moreover, you may use together other cooling methods, such as water cooling.

  The temperature of the cooling molding roll is preferably 20 ° C. or higher and 60 ° C. or lower. By controlling the temperature of the cooling roll to 60 ° C. or less, it is possible to suppress the formation of large β crystals and to prevent the roughening due to β crystals from occurring on the film surface during stretching, thereby obtaining high smoothness of the smooth surface. The (Sp), (Sq), and (Rpk) of the smooth surface in the A layer and the roughened surface in the B layer are preferable from the viewpoint of making the above range easier. In addition, the formation of large α crystals can be suppressed, and the transparency of the film can be improved. The uniformity of thickness can be improved by setting the temperature of the cooling molding roll to 20 ° C. or higher.

  Further, the resin layer in contact with the first cooling molding roll may be the outermost layer (A layer) on the smooth surface side to obtain high smoothness on the smooth surface side, and (Sp), (Sq) and ( Rpk) is preferable from the viewpoint of easily making the above range.

  In the cast sheet manufacturing process, the thickness of the cast sheet to be manufactured is not particularly limited, but is usually 0.5 to 5 mm.

(4) Stretching process In the stretching process, a biaxial stretching process is performed on the cast sheet obtained in the cast sheet manufacturing process. As the biaxial stretching method, both simultaneous biaxial stretching and sequential biaxial stretching can be employed.

  As an example of the sequential biaxial stretching method, first, the cast sheet is preferably kept at a temperature of 120 to 155 ° C. and passed between rolls provided with a speed difference, 4 to 7 times in the flow direction (longitudinal direction, MD direction). Is longitudinally stretched (longitudinal stretching step). Subsequently, the longitudinally stretched uniaxially stretched film was led to a tenter and preferably stretched at a temperature of 150 to 175 ° C. in a direction orthogonal to the flow direction (lateral direction, width direction, TD direction) 7 to 11 times. After (lateral stretching step), preferably at a temperature of 160 to 180 ° C., the transverse stretching ratio is relaxed and heat-fixed by about 5 to 10% (relaxation step).

  As an example of the simultaneous biaxial stretching method, the cast sheet is guided to a tenter, and preferably stretched 4 to 11 times in the flow direction at a temperature of 150 to 175 ° C. and 4 to 4 in the direction perpendicular to the flow direction. The film is stretched 11 times (stretching step), and preferably relaxed and heat-fixed at a temperature of 160 to 180 ° C. by about 5 to 10% in the ratio of longitudinal stretching and lateral stretching (relaxing step).

  By appropriately adjusting the temperature in each stretching step to the above range, stretching can be performed with good stretchability and thickness uniformity. Moreover, since the (Sp), (Sq), and (Rpk) of the smooth surface in the A layer and the roughened surface in the B layer tend to increase when the temperature in each stretching step is high, these are within the above-mentioned range. Thus, it is preferable to appropriately adjust the temperature in each stretching step.

  The relaxed and heat-set film is trimmed at the end and then wound up by a winder. The wound film is subjected to an aging treatment in an atmosphere of about 20 to 45 ° C. as necessary, and then cut to a desired product width.

  The film can be subjected to corona discharge treatment as necessary. Corona discharge treatment can adjust the adhesion between the smooth surface and the object to be protected or the adhesive when it is attached to the object to be protected, or can impart printability to the roughened surface. A known method can be employed for the corona discharge treatment.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show "mass part" and "mass%", respectively.
Further, various measurement methods and evaluation methods in Examples and Comparative Examples are as follows.

[Method for measuring characteristic value and method for evaluating effect]
(1) Polymer melt flow rate (MFR)
According to JIS K-7210 (1999), it measured using the Toyo Seiki Seisakusho make melt indexer. As described above, the measurement conditions were (i) a measurement temperature of 230 ° C. and a load of 21.18 N, or (ii) a temperature of 260 ° C. and a load of 49.05 N, depending on the melting point of the resin used.

(2) Mesopentad fraction of propylene polymer (mmmm)
The propylene polymer was dissolved in a solvent, and the mesopentad fraction (mmmm) was determined under the following conditions using a high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR).

Measuring instrument: JEOL Ltd., high temperature FT-NMR JNM-ECP500
Observation nucleus: 13C (125MHz)
Measurement temperature: 135 ° C
Solvent: Ortho-dichlorobenzene [ODCB: Mixed solvent of ODCB and deuterated ODCB (volume mixing ratio = 4/1)]
Measurement mode: Single pulse proton broadband decoupling Pulse width: 9.1 μsec (45 ° pulse)
Pulse interval: 5.5 sec
Integration count: 4500 shift standard: CH3 (mmmm) = 21.7 ppm
It calculated by the percentage (%) from the intensity | strength integral value of each signal originating in the combination (mmmm, mrrm, etc.) of a pentad (pentad). Regarding the attribution of each signal derived from mmmm, mrrm, etc., for example, the description of spectra such as “T. Hayashi et al., Polymer, 29, 138 (1988)” was referred to.

(3) Melting point of polymer Perkin Elmer, Inc. The measurement was performed under the following conditions using a Diamond DSC manufactured by the company.

  First, about 5 mg of the polymer is weighed, sealed in an aluminum sample holder, and set in a DSC apparatus. The temperature is raised from 30 ° C. to 280 ° C. at a rate of 20 ° C./min under a nitrogen flow and held for 5 minutes. Thereafter, the temperature is lowered to 30 ° C. at a rate of 20 ° C./min and held for 5 minutes. Next, the temperature is raised again at 20 ° C./minute, the melting peak of the crystal is measured, and the top temperature of the endothermic peak is measured. When showing a plurality of endothermic peaks, the temperature at the top of the maximum endothermic peak is measured. The above measurement was repeated three times, and the average value of the three points was taken as the melting point.

(4) Ash content of polymer and film It was measured with a measurement sample amount of 200 g according to JIS-K7250-1 (2006) A method.

(5) Surface shape of film (maximum peak height value (Sp), root mean square of height data (Sq), protruding peak height (Rpk) in load curve)
<Measurement>
Using the optical interference type non-contact surface shape measuring instrument (manufactured by Ryoka System Co., Ltd., non-contact surface / layer cross-sectional shape measurement system, VertScan (registered trademark) 2.0 (model: R5500 GML)) under the following conditions It was measured.

Measurement mode: WAVE
Filter: 530 white
Objective lens magnification: × 10
Field of view: 470.92 μm × 353.16 μm (640 × 480 pixels)
Number of measurements: measured at any 10 locations on the film surface <Image processing>
The following image processing was performed using the analysis software “VS-Viewer” for the measurement data at the 10 locations.

Noise removal processing: Median filter (5 × 5 pixels)
Roughness component extraction processing: Gaussian filter processing (cut-off value of 30 μm or more)
<Calculation of Sp, Sq, Rpk>
Each parameter of each of the 10 surface shape data images obtained by image processing as described above was measured using the analysis software “VS-Viewer”.
The maximum value of 10 values measured as the maximum peak height value was defined as (Sp).
The average value of 10 values measured as the root mean square value of the height data was defined as (Sq).
The average value of 10 values measured as the value of the protruding peak height in the load curve was defined as (Rpk).

(6) Thickness of film It measured based on JIS-C2330 using Citizen Seimitsu Co., Ltd. paper thickness measuring device MEI-11.

(7) Haze degree of film It measured based on JIS-K7136 using Nippon Denshoku Industries Co., Ltd. haze meter NDH-5000.

(8) Transparency of film It measured using transparency measuring instrument TM-1D by Murakami Color Research Laboratory. The minimum transparency was recorded.

(9) Number of fish eyes of film Using a fish eye counter manufactured by Frontier System Co., Ltd., the number of fish eyes having an area of 0.0045 mm ² or more was measured. Measurement is performed for the area of the measurement per 0.01351M ² once, the measurement performed 6 times, the fisheye number of obtained area 0.08106m ² obtained by summing the results, in terms of per 1 m ² did.

(10) Applicability of winding the film The wound film was suspended in the air at room temperature for one week while being wound, and then the presence or absence of the following problems was confirmed while rewinding with a winder. .

  Blocking: Adhesion between films is observed. If the film is severe, problems such as tearing or deformation occur when the film is rewound, or the film cannot be peeled off.

  Wrinkles: Wrinkles are seen in the film flow direction or width direction. If it is severe, it will not recover even after the film has been pulled out, resulting in poor bonding with the protected object.

Concavity and convexity: Concavity and convexity occur in the film due to air pools remaining unevenly inside the winding. If it is severe, it will not recover even after the film has been pulled out, resulting in poor bonding with the protected object.
(Criteria)
◎: Blocking, wrinkles, unevenness is not generated and can be used well. ○: Any of blocking, wrinkles, unevenness can be seen slightly, but it can be used. △: Any of blocking, wrinkles, unevenness is moderate. ： Difficult to use ×: Blocking, wrinkle, or unevenness is severe and cannot be used

(11) Transfer of the roughened surface to the smooth surface of the film Two 60 mm × 60 mm samples were cut out from the film, overlapped so that the roughened surface and the smooth surface were in contact, and both sides were smooth metal plates (200 mm × 200 mm ) To adjust the temperature to 30 ° C. Using MINI TEST PRESS-10 manufactured by Toyo Seiki Seisakusho Co., Ltd., 30 MPa was loaded for 10 minutes at 30 ° C., and then the generation (transfer) of dents on the smooth surface side was evaluated.

  Presence / absence of transfer is determined by an optical interference type non-contact surface shape measuring instrument (manufactured by Ryoka System Co., Ltd., non-contact surface / layer cross-sectional shape measurement system, VertScan (registered trademark) 2.0 (model: R5500GML)) Under the following conditions, the film surface was observed while applying interference light.

Measurement mode: WAVE
Filter: 530 white
Objective lens magnification: × 5
(Criteria)
◎: Depression caused by rough surface protrusion is not observed at all, and can be used well. ○: Recess is observed slightly slightly and rough surface protrusion, but can be used. △: Shallow dent due to rough surface protrusion is recognized and used. X: Deep dents due to roughened surface protrusions are clearly recognized and cannot be used

[Types of polymers used in Examples and Comparative Examples]
Propylene polymer A: manufactured by Prime Polymer Co., Ltd., MFR = 2.8 g / 10 min, (mmmm) = 93%, melting point = 164 ° C., ash content = 25 ppm, and calcium stearate 50 ppm as a neutralizing agent ( Isotactic polypropylene homopolymer)
Α-olefin polymer A: manufactured by Mitsui Chemicals, Inc., Toughmer BL3450, melting point 104 ° C., MFR = 12 g / 10 minutes (1-butene / ethylene copolymer)
Α-olefin polymer B: manufactured by Mitsui Chemicals, Inc., Toughmer XM7070, melting point 75 ° C., MFR = 7 g / 10 min (1-butene / propylene copolymer)
Α-olefin polymer C: manufactured by Mitsui Chemicals, Inc., TPX MX002O, melting point 224 ° C., MFR = 21 g / 10 min (4-methyl-1-pentene polymer)
Α-olefin polymer D: manufactured by Mitsui Chemicals, Inc., TPX DX845, melting point 232 ° C., MFR = 9 g / 10 min (4-methyl-1-pentene polymer)
Example 1
(1) Preparation Step, Extrusion / Filtration Step / Layer A After propylene polymer A resin pellets are put into a single screw extruder from a hopper and melt extruded at a resin temperature of 230 ° C. with a discharge rate of 5 kg / unit time. Then, using a sintered metal nonwoven fabric (fiber sintered body) as a filter medium, filtration was performed with a polymer filter using a disk filter manufactured by Nagase Sangyo Co., Ltd. having a filtration accuracy of 10 μm to obtain a filtrate.
Intermediate layer: 99 parts of propylene polymer A and 1 part of a master batch containing 2% of Rikaclear PC1 manufactured by Shin Nippon Rika Co., Ltd. as an organic crystal nucleating agent were mixed in a dry blend apparatus.

The mixed raw material is put into a single screw extruder from a hopper and melt extruded at a resin temperature of 230 ° C. at a discharge rate of 18 kg / unit time. Then, a sintered metal nonwoven fabric (fiber sintered body) is used as a filter medium, and the filtration accuracy is 10 μm. The product was filtered through a polymer filter using a disk filter manufactured by Nagase Sangyo Co., Ltd. to obtain a filtrate.
-B layer Propylene-type polymer A88 part and (alpha) -olefin type polymer A12 part were mixed in the dry blend apparatus.

The mixed raw material is put into a single screw extruder from a hopper and melt extruded at a resin temperature of 230 ° C. at a discharge rate of 2 kg / unit time. Then, a sintered metal nonwoven fabric (fiber sintered body) is used as a filter medium, and the filtration accuracy is 10 μm. The product was filtered through a polymer filter using a disk filter manufactured by Nagase Sangyo Co., Ltd. to obtain a filtrate.
(2) Cast sheet manufacturing process Each resin composition (filtrate) forming the A layer, the intermediate layer, and the B layer obtained in the above process was laminated in this order by a confluence apparatus, and then extruded from a T-die. . The extruded laminated resin is pressed with an air knife from the B layer side so that the A layer is in contact with a cooling molding roll whose surface temperature is adjusted to 40 ° C., and then the B layer is the second stage having a surface temperature of 30 ° C. It was pressed against a cooling molding roll and solidified by cooling to obtain a cast sheet having a thickness of about 1.2 mm.
(3) Stretching process The cast sheet obtained in the above process was brought into contact with a metal roll and heated to 130 ° C., and then stretched 4.5 times between rolls having a difference in peripheral speed. Next, the uniaxially stretched film is introduced into a hot air oven while being sandwiched between clips, preheated to 165 ° C., then stretched 10 times, and then heat fixed at 170 ° C. while relaxing 10% in the width direction. A biaxially stretched polypropylene film having a thickness of 25 μm was obtained. The obtained biaxially stretched polypropylene film was wound up after trimming the ends.

  The surface roughness of the obtained biaxially stretched polypropylene film was evaluated, and the results are shown in Table 2. Further, the total thickness, haze, transparency, ash content, number of fish eyes, rollability, and transfer of the roughened surface to a smooth surface were evaluated. The results are shown in Table 3.

Example 2
The total thickness is the same as in Example 1 except that the contents of the propylene-based polymer A and the α-olefin-based polymer A in the resin composition forming the B layer are changed as shown in Table 1. A 25 μm biaxially stretched polypropylene film was obtained. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

Example 3
A biaxially stretched polypropylene film having a total thickness of 25 μm was obtained in the same manner as in Example 1 except that the α-olefin polymer A in the resin composition forming the B layer was changed to the olefin polymer B. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

Example 4
As shown in Table 1, the α-olefin polymer A in the resin composition forming the B layer is changed to the olefin polymer C, and the contents of the propylene polymer A and the α-olefin polymer C are shown in Table 1. In the same manner as in Example 1 except that the resin temperature at the time of extrusion by a single screw extruder was 250 ° C. and the heating temperature at the time of longitudinal stretching was 145 ° C., biaxial stretching with a total thickness of 25 μm A polypropylene film was obtained. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

Example 5
As shown in Table 1, the olefin polymer A in the resin composition forming the B layer is changed to α-olefin polymer D, and the contents of propylene polymer A and α-olefin polymer D are shown in Table 1. A biaxially stretched polypropylene film having a total thickness of 25 μm was obtained in the same manner as in Example 4 except that it was changed to. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

Comparative Example 1
The olefin polymer A in the resin composition forming the B layer is high density polyethylene (Hi-Zex7000F, Prime Polymer Co., Ltd., melting point 130 ° C.), and the contents of the propylene polymer A and high density polyethylene are as follows. A biaxially stretched polypropylene film having a total thickness of 25 μm was obtained in the same manner as in Example 4 except that the changes were made as shown in Table 1. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

Comparative Example 2
In the resin composition for forming the B layer, a biaxial shaft having a total thickness of 25 μm was prepared in the same manner as in Example 1 except that the α-olefin-based polymer was not blended and the heating temperature during longitudinal stretching was 140 ° C. A stretched polypropylene film was obtained. The evaluation results of the obtained biaxially stretched polypropylene film are shown in Tables 2 and 3.

  As is clear from the results of Examples 1 to 5, the biaxially stretched polypropylene film of the present invention has an appropriate surface roughness on the smooth surface and the roughened surface. The rough surface transfer is also good. In addition, it has few fish eyes and is excellent in haze and transparency.

  However, in Comparative Example 1 using high-density polyethylene instead of the α-olefin polymer, the surface roughness of the roughened surface is not appropriate, the transfer of the roughened surface to the smooth surface is poor, haze degree and The transparency also tended to be inferior. Moreover, the biaxially stretched polypropylene film of Comparative Example 2 that did not use the α-olefin polymer had a problem in winding ability because the surface roughness of the roughened surface was not appropriate.

  The biaxially stretched polypropylene film of the present invention is a release film or release liner used in the production process of electronic parts, electronic substrates, the production process of thermosetting resin members such as fiber reinforced plastic, the production process of photosensitive film, etc. It can be suitably used for a carrier, a protective material, a separator film thereof, and the like at the time of manufacturing the material.

Claims (10)

A laminated film having an outermost layer A layer and an outermost layer B layer having different surface roughnesses,
A layer is formed from a resin composition containing a propylene polymer, and satisfies the following (a) to (c),
(A) The value (Sp) of the maximum peak height of the outer surface is 0.1 μm or less,
(B) The root mean square (Sq) of the height data of the outer surface is 0.01 μm or less, and (c) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01 μm. Less than,
B layer is formed from the resin composition containing a propylene polymer and an α-olefin polymer, and the following (d) to (f):
(D) The value (Sp) of the maximum peak height of the outer surface is 0.5 μm or less,
(E) The root mean square (Sq) of the height data of the outer surface is 0.01 to 0.05 μm, and (f) the protruding peak height (Rpk) in the load curve obtained from the roughness curve of the outer surface is 0.01-0.05 μm,
Meet the,
Having at least one intermediate layer between the A layer and the B layer,
Biaxially stretched polypropylene film. The biaxially oriented polypropylene film according to claim 1 , wherein the intermediate layer is formed from a resin composition containing a propylene-based polymer. The biaxially stretched polypropylene film according to claim 1 or 2 , wherein the total thickness is 10 to 150 µm. The biaxially stretched polypropylene film according to any one of claims 1 to 3 , comprising 5 to 30% by mass of an α-olefin polymer in the resin composition forming the B layer. The biaxially stretched polypropylene film according to any one of claims 1 to 4 , wherein the α-olefin polymer contained in the resin composition forming the B layer is a butene polymer. The biaxially stretched polypropylene film according to claim 5 , wherein the butene polymer is a 1-butene / ethylene copolymer. The biaxially stretched polypropylene according to any one of claims 1 to 4 , wherein the α-olefin polymer contained in the resin composition forming the B layer is a 4-methyl-1-pentene polymer. the film. The biaxially stretched polypropylene film according to any one of claims 1 to 7 , wherein the ash content in the film is 100 ppm or less. The number of fish eyes having an area of 0.0045 mm ² or more is 700 pieces / m ² or less.
The biaxially stretched polypropylene film according to any one of claims 1 to 8 . A method of manufacturing a biaxially oriented polypropylene film according to any one of claims 1 to 9 following steps (i) ~ (iv);
(I) A layer and B layer, and the step of preparing a resin composition for forming the intermediate layer,
(Ii) a step of filtering the resin composition obtained in step (i) after extrusion,
(Iii) a step of laminating and molding the resin composition obtained in step (ii) to obtain a cast sheet;
(Iv) a step of biaxially stretching the cast sheet obtained in step (iii);
And in the step (ii), filtration is performed with a filter having a filtration accuracy of 20 μm or less.

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